Dental compositions comprising a fatty mono(meth)acrylate

ABSTRACT

Presently described are dental compositions comprising one or more fatty mono(meth)acrylates, methods of use, dental articles, and methods of making dental compositions. It has been found that a relatively low concentration of a fatty mono(meth)acrylate can improve the handling characteristics of a dental composition by reducing the tendency of the composition to stick to a dental instrument and/or by reducing the tendency of a dental composition to string when being manipulated by a dental instrument. In one embodiment, a hardenable dental composition is described comprising a polymerizable resin composition comprising at least one multifunctional ethylenically unsaturated monomer; 0.2 to 10 wt-% of one or more fatty mono(meth)acrylate monomers; and at least 50 wt-% of inorganic oxide filler.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/111,376, filed Oct. 11, 2013, which is a national stage filing under35 U.S.C. 371 of International Application No. PCT/US2012/0442902012,filed Jun. 27, 2012, which claims benefit of U.S. ProvisionalApplication No. 61/502,500 filed Jun. 29, 2011.

SUMMARY

Although various dental compositions have been described, industry wouldfind advantage in (e.g. restoration) materials having improvedproperties such as improved handling characteristics.

In one embodiment, a method of making a dental composition is described.The method comprises providing a hardenable dental composition whereinthe dental composition exhibits tackiness or stringiness whenmanipulated with a dental instrument; and adding a sufficient amount ofone or more fatty mono(meth)acrylate monomer such that the tackiness orstringiness is substantially reduced. In some embodiments, the fattymono(meth)acrylate monomer comprises an alkyl group having greater than12 carbon atoms. In this embodiment, the fatty mono(meth)acrylatemonomer can be present in the polymerizable resin composition in anamount up to 15 wt-%. In other embodiments, the fatty mono(meth)acrylatemonomer comprises an alkyl group having 6 to 12 carbon atoms. In thisembodiment, the fatty mono(meth)acrylate monomer is present in thepolymerizable resin composition in an amount up to 20 wt-%.

In one favored embodiment, the hardenable dental composition is a dentalrestoration material comprising an appreciable amount (e.g. at least 50wt-%) of inorganic oxide filler. In this embodiment, the hardenabledental composition typically comprises 0.2 to 10 wt-% of a fattymono(meth)acrylate monomer(s). Such hardenable dental compositiontypically comprises at least one multifunctional ethylenicallyunsaturated monomer.

In another embodiment, a method of treating a tooth surface isdescribed. The method comprises providing a hardenable dentalcomposition comprising one or more fatty mono(meth)acrylate monomers asdescribed herein; placing the hardenable dental composition on a toothsurface; and hardening the hardenable dental composition.

Dental restoration materials can be utilized to form a dental article(e.g. such as a crown). Thus, in another embodiment dental articles aredescribed comprising the hardenable dental composition, as describedherein, at least partially hardened.

Each of these embodiments may further be characterized by any one orcombination of various features, as described herein. The hardenabledental composition is typically sufficiently flowable such that thecomposition can be extruded through an orifice with a force no greaterthan 20 kg for an orifice diameter of 2 mm. The fatty mono(meth)acrylatemonomer phase separates from the polymerizable resin composition suchthat the fatty mono(meth)acrylate forms microscopic domains. Such phaseseparation may increase the contrast ratio of the hardenable dentalcomposition by at least 5. In some embodiments, the composition has acontrast ratio of at least 45, yet can be free of opacifying pigment. Insome embodiments, the composition has a ratio of contrast ratio to depthof cure of at least 10.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a transmission electron microscopy image of a cross-section ofan embodied cured dental composition.

DETAILED DESCRIPTION

As used herein, “dental composition” refers to a material, optionallycomprising filler, capable of adhering or being bonded to an oralsurface.

“Hardenable” and “curable’ are descriptive of a material or compositionthat can be cured (e.g., polymerized or crosslinked) by heating toinduce polymerization and/or crosslinking; irradiating with actinicirradiation to induce polymerization and/or crosslinking; and/or bymixing one or more components to induce polymerization and/orcrosslinking. “Mixing” can be performed, for example, by combining twoor more parts and mixing to form a homogeneous composition.Alternatively, two or more parts can be provided as separate layers thatintermix (e.g., spontaneously or upon application of shear stress) atthe interface to initiate polymerization.

A curable dental composition can be used to bond a dental article to atooth structure, be used as a restorative that is placed directly intothe mouth and cured in-situ, or alternatively be used to fabricate aprosthesis outside the mouth that is subsequently adhered within themouth.

Curable dental compositions include, for example, adhesives (e.g.,dental and/or orthodontic adhesives), cements (e.g., resin-modifiedglass ionomer cements, and/or orthodontic cements), liners (applied tothe base of a cavity to reduce tooth sensitivity), and resinrestoratives (also referred to as direct composites) such as dentalfillings, as well as crowns, bridges, and articles for dental implants.Highly filled dental compositions are also used for mill blanks, fromwhich a crown may be milled. A composite or dental restoration materialis a highly filled paste designed to be suitable for filling substantialdefects in tooth structure. Dental cements are somewhat less filled andless viscous materials than composites, and typically act as a bondingagent for additional materials, such as inlays, onlays and the like, oract as the filling material itself if applied and cured in layers.Dental cements are also used for permanently bonding dental restorationssuch as a crown or bridge to a tooth surface or an implant abutment.

“Hardened” refers to a material or composition that has been cured(e.g., polymerized or crosslinked).

“Hardener” refers to something that initiates hardening of a resin. Ahardener may include, for example, a polymerization initiator system, aphotoinitiator system, a thermal initiator and/or a redox initiatorsystem.

“Shrinkage” refers to the volumetric change as a result of curing, i.e.shrinkage that occurs after gelation as can be measured using the WattsShrinkage (Watts) test method as described in WO2011/126647. Hence,shrinkage does not refer to the volumetric change that occurs prior togelation.

“Dental article” refers to an article that can be adhered (e.g., bonded)to a tooth structure or dental implant. Dental articles include, forexample, crowns, bridges, veneers, inlays, onlays, fillings, orthodonticappliances and devices.

“Orthodontic appliance” refers to any device intended to be bonded to atooth structure, including, but not limited to, orthodontic brackets,buccal tubes, lingual retainers, orthodontic bands, bite openers,buttons, and cleats. The appliance has a base for receiving adhesive andit can be a flange made of metal, plastic, ceramic, or combinationsthereof. Alternatively, the base can be a custom base formed from curedadhesive layer(s) (i.e. single or multi-layer adhesives).

“Oral surface” refers to a soft or hard surface in the oral environment.Hard surfaces typically include tooth structure including, for example,natural and artificial tooth surfaces, bone, and the like.

“(Meth)acrylate” is a shorthand reference to acrylate, methacrylate, orcombinations thereof; “(meth)acrylic” is a shorthand reference toacrylic, methacrylic, or combinations thereof; and “(meth)acryl” is ashorthand reference to acryl, methacryl, or combinations thereof.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

Presently described are dental compositions comprising one or more fattymono(meth)acrylates, methods of use, dental articles, and methods ofmaking dental compositions.

It has been found that a relatively low concentration of a fattymono(meth)acrylate can improve the handling characteristics of a dentalcomposition by reducing the tendency of the composition to stick to adental instrument and/or by reducing the tendency of a dentalcomposition to string when being manipulated by a dental instrument.

Without intending to be bound by theory, it is surmised that the fattymono(meth)acrylate(s) phase separates during use. Evidence of such phaseseparation can be detected using transmission microscopy. With referenceto FIG. 1, a transmission electron microscopy image of a cross-sectionof an embodied cured dental composition, the fatty mono(meth)acrylatephase separates to form microscopic domains 100, on the order ofmagnitude of about 0.5 to 1 micron. Hence, such phase separation istypically not a “bulk” phase separation as would result in the fattymono(meth)acrylate forming a separate layer that can be redispersed inthe polymerizable resin composition. Such phase separation is amenableto increasing the opacity or contrast ratio, with or without opacifyingpigments. In some embodiments, the addition of the fattymono(meth)acrylate(s) to an (e.g. unpigmented) polymerizable resin ofthe hardenable dental composition increases the contrast ratio by atleast 5, or 10, or 15, or 20.

By increasing the opacity or contrast ratio, the concentration ofopacifying pigments can be reduced. In some embodiments, the hardenabledental composition may be free of opacifying pigments. Reducing theconcentration of pigments can improve the depth of cure. In someembodiments, the (e.g. filled) dental compositions described hereinexhibit a ratio of contrast ratio to depth of cure of at least 10, 11,12, 13, 14, or 15. This ratio is typically no greater than 25 or 20.

The fatty mono(meth)acrylate comprises a straight chain or branchedalkyl group having greater than 5 carbon atoms. The alkyl group mayoptionally comprise substituents provided that the substituted alkylgroup remains substantially hydrophobic.

In some embodiments, the fatty mono(meth)acrylate monomer comprises analkyl group having at least 6, or 7, or 8 carbon atoms and no greaterthan 12 carbon atoms. In this embodiment, the fatty mono(meth)acrylatemonomer is present in the polymerizable resin composition in an amountup to 20 or 25 wt-%. In other embodiments, the fatty mono(meth)acrylatemonomer comprises an alkyl group having greater than 12 carbon atoms. Inthis embodiment, the fatty mono(meth)acrylate monomer can be present inthe polymerizable resin composition in an amount up to 15 wt-%. Thechain length of the alkyl group (i.e. R) is typically no greater than 50carbons atoms or 40 carbons. As the chain length of the alkyl groupincrease, the melt point tends to also increase. In some embodiments,the chain length of the alkyl group is no greater than 35, or 30, or 25carbon atoms.

Various fatty mono(meth)acrylates are commercially available. Fattymono(meth)acrylates can be formed by reacting the hydroxyl group of afatty alcohol or derivative thereof with a (meth)acrylic acid, a(meth)acryloyl halide, or a hydroxyl-reactive (meth)acrylate compound.Various fatty alcohols are known including dodecyl alcohol, cetylalcohol CH₃(CH₂)₁₅OH, stearyl alcohol (also known as octadecyl alcoholor 1-octadecanol), and oleyl alcohol.

Without intending to be bound by theory, it is surmised that the chainlength of the alkyl group (i.e. R) may relate to the rate of phaseseparation. For example, fatty mono(meth)acrylates comprising longerchain alkyl groups may phase separate faster than fattymono(meth)acrylates comprising shorter alkyl groups.

The fatty mono(meth)acrylate preferably has a melt point no greater thanabout 30° C. In some embodiments, the fatty mono(meth)acrylate is aliquid at 25° C. One favored fatty mono(meth)acrylate is stearylmethacrylate, having a melt point of 23° C.

The hardenable dental composition is preferably a dental restorationmaterial comprising an appreciable amount of inorganic oxide filler. Theconcentration of fatty mono(meth)acrylate(s) in the filled polymerizableresin composition is typically at least 0.2, or 0.3, or 0.4, or 0.5 wt-%and generally no greater than 15 wt-%, 14 wt-%, 13 wt-%, 12 wt-%, 11wt-%, or 10 wt-%. In some embodiments, the concentration of fattymono(meth)acrylate(s) in the filled polymerizable resin composition isno greater, than 9 wt-% or 8 wt-% or 7 wt-% or 6 wt-% or 5 wt-%. Aconcentration of about 1 wt-% to about 5 wt-% can be preferred forembodiments wherein the that fatty mono(meth)acrylate is stearylmethacrylate. However, when the chain length is greater than 18 carbonatoms, a lower concentration may be suitable. Further, when the chainlength is less than 18 carbon atoms, higher concentrations may be neededto obtain the desired result. As the concentration of fattymono(meth)acrylate increases, the mechanical properties, such asDiametral Tensile Strength, can decrease. Hence, in some embodiments, itis preferred to utilize the minimum concentration that will provideimproved handling properties (e.g. sufficient reduction in tack and/orstringing). However, as the concentration of fatty mono(meth)acrylateincreases, the contrast ratio typically also increases. When thistechnical effect is desired it may be preferred to utilize a higherconcentration than the “minimal” concentration provided that theDiametral Tensile Strength is at least 50 MPa, 55 MPa or 60 MPa.

The fatty mono(meth)acrylate is typically present as phase separatedmicroscopic domains, as previously described. For embodiments whereinthe fatty mono(meth)acrylate has a melt point above ambient temperature20-25° C., the fatty mono(meth)acrylate is present as solid domainswithin a flowable liquid polymerizable resin composition. In the absenceof heat or pressure, a flowable liquid generally forms to the shape ofits container within minutes or hours. Hence, a mixture of the fattymono(meth)acrylate dispersed within the polymerizable resin compositionis not a solid, or semi-solid having a wax-like consistency.

Regardless of the melt point, the fatty mono(meth)acrylate(s) isgenerally initially dissolved or dispersed in the unfilled or filledpolymerizable resin composition. For embodiments wherein the fattymono(meth)acrylate has a melt point above room temperature, the (e.g.unfilled or filled) polymerizable resin composition is typicallysufficiently heated such that the fatty (mono)methacrylate is a liquid,rather than a solid. Heating can also reduce the viscosity of other theother polymerizable components of the polymerizable resin, which in turncan also aid in dispersing the fatty mono(meth)acrylate.

In some embodiments, the filled hardenable dental composition is alsosufficiently flowable such that it can be dispensed from a narrow-tipsyringe, typically 20 gauge or similar, under hand pressure. In otherembodiments, the hardenable dental composition can be extruded throughan orifice with a force no greater than 20 kg for an orifice diameter of2 mm. In some embodiments, the extrusion force is no greater than 15, or14, or 13, or 12, or 11, or 10 kg. The extrusion force is typically atleast 1 or 2 kg and in some embodiments, at least 3, 4, or 5 kg.

The hardenable (e.g. dental) compositions described herein furthercomprise at least one ethylenically unsaturated monomer or oligomer incombination with the fatty mono(meth)acrylate. In some embodiments, suchas dental restorations the ethylenically unsaturated monomer ismultifunctional. The phrase “multifunctional ethylenically unsaturated”means that the monomers each comprise at least two ethylenicallyunsaturated (e.g. free radically) polymerizable groups, such as(meth)acrylate groups.

In favored embodiments, such ethylenically unsaturated group is a (e.g.terminal) free radically polymerizable group including (meth)acryl suchas (meth)acrylamide (H₂C═CHCON— and H₂C═CH(CH₃)CON—) and(meth)acrylate(CH₂CHCOO— and CH₂C (CH₃)COO—). Other ethylenicallyunsaturated polymerizable groups include vinyl (H₂C═C—) including vinylethers (H₂C═CHOCH—). The ethylenically unsaturated terminalpolymerizable group(s) is preferably a (meth)acrylate group,particularly for compositions that are hardened by exposure to actinic(e.g. UV) radiation. Further, methacrylate functionality is typicallypreferred over the acrylate functionality in curable dentalcompositions.

The ethylenically unsaturated monomer may comprise various ethylenicallyunsaturated monomers, as known in the art, for use in dentalcompositions.

In some favored embodiments, the (e.g. dental) composition comprises oneor more ethylenically unsaturated (e.g. (meth)acrylate) monomers havinga low volume shrinkage monomer. Preferred (e.g. filled) dentalcompositions (useful for restorations such as fillings and crowns)described herein comprise one or more low volume shrinkage monomers suchthat the composition exhibits a Watts Shrinkage of less than about 2%.In some embodiments, the Watts Shrinkage is no greater than 1.90%, or nogreater than 1.80%, or no greater than 1.70%, or no greater than 1.60%.In favored embodiments, the Watts Shrinkage is no greater than 1.50%, orno greater than 1.40%, or no greater than 1.30%, and in some embodimentsno greater than 1.25%, or no greater than 1.20%, or no greater than1.15%, or no greater than 1.10%.

Preferred low volume shrinkage monomers include isocyanurate monomers,such as described in WO2011/126647; polymerizable monomers described inWO2012/003136; polymerizable compounds having at least one cyclicallylic sulfide moiety such as described in US2008/0194722; methylenedithiepane silanes as described in U.S. Pat. No. 6,794,520; oxetanesilanes such as described in U.S. Pat. No. 6,284,898; and di-, tri,and/or tetr-(meth)acryloyl-containing materials such as described inWO2008/082881; each of which are incorporated herein by reference.

It has been found that polymerizable resin composition comprising lowvolume shrinkage monomers such as isocyanurate monomers and/orethoxylated resorcinol monomers exhibit the desired phase separationwhen combined with a fatty mono(meth)acrylate(s), as described herein.

In some embodiments, the majority of the (e.g. unfilled) polymerizableresin composition comprises one or more low volume shrinkage monomers.For example, at least 50%, 60%, 70%, 80%, 90% or more of the (e.g.unfilled) polymerizable resin may comprise low volume shrinkagemonomer(s).

In one embodiment, the dental composition comprises at least oneisocyanurate monomer. The isocyanurate monomer generally comprises atrivalent isocyanuric acid ring as an isocyanurate core structure and atleast two ethylenically unsaturated (e.g. free radically) polymerizablegroups bonded to at least two of the nitrogen atoms of the isocyanuratecore structure via a (e.g. divalent) linking group. The linking group isthe entire chain of atoms between the nitrogen atom of the isocyanuratecore structure and the terminal ethylenically unsaturated group. Theethylenically unsaturated (e.g. free radically) polymerizable groups aregenerally bonded to the core or backbone unit via a (e.g. divalent)linking group.

The trivalent isocyanurate core structure generally has the formula:

The divalent linking group comprises at least one nitrogen, oxygen orsulfur atom. Such nitrogen, oxygen or sulfur atom forms an urethane,ester, thioester, ether, or thioether linkage. Ether and especiallyester linkages can be beneficial over isocyanurate monomers comprisingurethane linkages for providing improved properties such as reducedshrinkage, and/or increased mechanical properties, e.g., diametraltensile strength (DTS). Thus, in some embodiments, the divalent linkinggroups of the iscosyanurate monomer are free of urethane linkages. Insome favored embodiments, the divalent linking group comprises an esterlinkage such as an aliphatic or aromatic diester linkage.

The isocyanurate monomer typically has the general structure

wherein R₁ is a straight chain, branched or cyclic alkylene, arylene, oralkarylene, optionally including a heteroatom (e.g. oxygen, nitrogen, orsulfur); R₂ is hydrogen or methyl; Z is alkylene, arylene, or alkarylenelinking group comprising at least one moiety selected from urethane,ester, thioester, ether, or thioether, and combinations of suchmoieties; and at least one of R₃ or R₄ is

R₁ is typically a straight chain, branched or cyclic alkylene,optionally including a heteroatom, having no greater than 12 carbonsatoms. In some favored embodiments, R₁ has no greater than 8, 6, or 4carbon atoms. In some favored embodiments, R₁ comprises at least onehydroxyl moiety.

In some embodiments, Z comprises an aliphatic or aromatic ester linkagesuch as a diester linkage.

In some embodiment, Z further comprises one or more ether moieties.Hence, the linking group may comprise a combination of ester or diestermoieties and one or more ether moieties.

For embodiments, wherein the isocyanurate monomer is a di(meth)acrylatemonomer, R₃ or R₄ is hydrogen, alkyl, aryl, or alkaryl, optionallyincluding a heteroatom.

R₁ is generally derived from the starting (e.g. hydroxy terminated)isocyanurate precursor. Various isocyanurate precursor materials arecommercially available from TCI America, Portland, Oreg. The structuresof exemplary isocyanurate precursor materials are depicted as follows:

The isocyanurate (meth)acrylate monomers disclosed herein having alinking groups comprising an oxygen atom of an ester moiety weregenerally prepared by reaction of hydroxy or epoxy terminatedisocyanurates with (meth)acrylated carboxylic acids such asmono-(2-methacryloxyethyl)phthalic acid andmono-(2-methacryloxytheyl)succinic acid.

Suitable (meth)acrylated carboxylic acids include for examplemono-(2-methacryloxyethyl)phthalic acid(s),mono-(2-methacryloxytheyl)succinic acid, andmono-(2-methacryloxyethyl)maleic acid. Alternatively, the carboxylicacid may comprise (meth)acrylamido functionally such as methacrylamidoderivatives of naturally occurring amino acids such asmethacrylamidoglycine, methacrylamidoleucine, methacrylamidoalanine etc.

In some embodiments, a single(meth)acrylated carboxylic acid is reactedwith a single hydroxyl terminated isocyanurate (e.g.tris-(2-hydroxylethyl)isocyanurate). When a sufficient molar ratio of(meth)acrylate carboxylic acid is utilized such that all the hydroxylgroups of the ring are reacted, such synthesis can produce a singlereaction product wherein each of the free radically terminated groups,bonded to the nitrogen atoms of the trivalent isocyanuric acid ring, arethe same. However, when a single epoxy terminated isocyanurate isreacted with a single carboxylic acid, the reaction product generallycomprises more than one isomer in the reaction product.

When two different hydroxy or epoxy terminated isocyanurates and/or twodifferent (e.g. (meth)acrylated) carboxylic acids are utilized, astatistical mixture of reaction products are obtained based on therelative amounts of reactants. For example, when a mixture of a(meth)acrylated aromatic carboxylic acid and a (meth)acrylate aliphaticcarboxylic acid are utilized, some of the free radically terminateddivalent linking groups bonded to the nitrogen atom of the trivalentisocyanuric acid ring comprise an aromatic group, whereas others do not.Further, when a combination (e.g. 1 equivalent) of a hydroxyl terminatedcarboxylic acid and (e.g. 2 equivalents) of a monocarboxylic acid (suchas octanoic acid) is reacted with a single hydroxyl terminatedisocyanurate (e.g. tris-(2-hydroxylethyl)isocyanurate), amono(meth)acrylate isocyanurate can be prepared as further described inWO2011/126647. Such mono(meth)acrylate isocyanurate is suitable for useas a reactive diluent.

Alternatively, isocyanurate (meth)acrylate monomers having ether groupcontaining linking groups can be synthesized. For example, in oneillustrative synthesis, phthalic acid anhydride can be reacted with amono-methacrylated di, tri, tetra or polyethylenegylcol in the presenceof a catalytic amount of 4-(dimethylamino)pyridine (DMAP) and butylatedhydroxytoluene inhibitor (BHT) at 95° C. for a 3-6 hours to form amono-methaycrylated polyethyleneglycol phthalic acid mono-ester. Theobtained methacrylated acid can be reacted, in acetone, withtris-(2-hydroxyethyl)isocyanurate using dicyclohexyl carbodiimide (DCC)at 0-5° C. then at room temperature. Such reaction scheme is depicted asfollows:

In another illustrative synthesis, tris(2-hydroxyethyl)isocyanurate canbe reacted with ethylene oxide to form a polyethylene glycol terminatedwith a hydroxyl group. The OH termini can be esterified withmeth(acrylic) acid to provide a product where the linking group is apolyether. Such reaction scheme is depicted as follows:

The isocyanurate monomer is preferably a multi(meth)acrylate such as adi(meth)acrylate isocyanurate monomer or a tri(meth)acrylateisocyanurate monomer.

The di(meth)acrylate monomer has the general structure:

wherein R₁, R₂, R₃ and Z are as previously described; R₆ is a straightchain, branched, or cyclic alkylene, arylene, or alkarylene, optionallyincluding a heteroatom (e.g. oxygen, nitrogen, or sulfur); and Y isalkylene, arylene, or alkarylene linking group comprising at least onemoiety selected from urethane, ester, thioester, ether, or thioether,and combinations of such moieties.

Illustrative di(meth)acrylate isocyanurate monomers includes:

In some favored embodiments, the tri(meth)acrylate monomer has thegeneral structure:

whereinR₁, R₅, and R₆ are independently a straight chain, branched, or cyclicalkylene, arylene, or alkarylene, optionally including a heteroatom(e.g. oxygen, nitrogen, or sulfur); R₂ is hydrogen or methyl; X, Y, andZ are independently alkylene, arylene, or alkarylene linking groupcomprising at least one moiety selected from urethane, ester, thioester,ether, thioether, or combinations of such moieties; and R₂ is hydrogenor methyl.

In some embodiments, R₁, R₅, and R₆ comprise at least one hydroxylmoiety.

Illustrative tri(meth)acrylate isocyanurate monomers include forexample:

The polymerizable resin portion of the hardenable unfilled dentalcomposition described herein may comprise at least 10 wt-%, 15 wt-%, 20wt-%, or 25 wt-%, multifunctional ethylenically unsaturated isocyanuratemonomer(s). The isocyanurate monomer may comprise a single monomer or ablend of two or more isocyanurate monomers. The total amount ofisocyanurate monomer(s) in the unfilled polymerizable resin portion ofthe hardenable (i.e. polymerizable) dental composition is typically nogreater than 90 wt-%, 85 wt-%, 80 wt-%, or 75 wt-%.

The filled hardenable dental composition described herein typicallycomprises at least 5 wt-%, 6 wt-%, 7 wt-%, or 8 wt-% of multifunctionalethylenically unsaturated isocyanurate monomer(s). The total amount ofisocyanurate monomer(s) of the filled hardenable (i.e. polymerizable)dental composition is typically no greater than 20 wt-%, or 19 wt-%, or18 wt-%, or 17 wt-%, or 16 wt-%, or 15 wt-%.

In some embodiments, the composition comprises a multifunctionalethylenically unsaturated isocyanurate monomer and a low volumeshrinkage monomer as described in previously cited WO2012/003136, suchas a multifunctional ethylenically unsaturated ethoxylated resorcinol(ER) monomer. Ethoxylated resorcinol (ER) monomers generally have thecore structure (i.e. backbone unit (U):

Such ethoxylated resorcinol (ER) monomers can be prepared for examplefrom starting materials such as

The backbone unit (U) typically comprises one or two spacer unit(s) (S)bonded to the backbone unit via an ether linkage. In some embodiments,the spacer unit(s) S typically comprises

wherein M=acroyl, methacroyl or phenyl.“G” may comprise a moiety selected from

as well as combinations and mixtures of such “G” moieties.

Some illustrative species of such multifunctional ethylenicallyunsaturated ethoxylated resorcinol (ER) monomers are described in thefollowing table:

In some embodiments, the (i.e. calculated) molecular weight of the lowshrink (e.g. isocyanurate and ethoxylated resorcinol) monomers istypically no greater than 2000 g/mole. In some embodiments, themolecular weight of the monomers is no greater than about 1500 g/mole or1200 g/mole or 1000 g/mole. The molecular weight of the monomers istypically at least 600 g/mole.

The ethylenically unsaturated monomers of the dental composition aretypically stable liquids at about 25° C. meaning that the monomer do notsubstantially polymerize, crystallize, or otherwise solidify when storedat room temperature (about 25° C.) for a typical shelf life of at least30, 60, or 90 days. The viscosity of the monomers typically does notchange (e.g. increase) by more than 10% of the initial viscosity.

Particularly for dental restoration compositions, the ethylenicallyunsaturated monomers generally have a refractive index of at least 1.50.In some embodiments, the refractive index is at least 1.51, 1.52, 1.53,or greater. The inclusion of sulfur atoms and/or the present of one ormore aromatic moieties can raise the refractive index (relative to thesame molecular weight monomer lacking such substituents).

In some embodiments, the (unfilled) polymerizable resin may comprisesolely one or more low shrink monomers in combination with the one ormore fatty mono(meth)acrylate(s). In other embodiments, the (unfilled)polymerizable resin further comprises (e.g. a small concentration of)other monomer(s). By “other” is it meant an ethylenically unsaturatedmonomer such as a (meth)acrylate monomer that is not a low volumeshrinkage monomer.

The concentration of such other monomer(s) is typically no greater than20 wt-%, 19 wt-%, 18 wt-%, 17 wt-%, 16 wt-%, or 15 wt-% of the(unfilled) polymerizable resin portion. The concentration of such othermonomers is typically no greater than 5 wt-%, 4 wt-%, 3 wt-%, or 2 wt-%of the filled polymerizable dental composition.

In some embodiments, the dental composition comprises a low viscosityreactive (i.e. polymerizable) diluent. Reactive diluents are typicallyrelatively low in molecular weight, having a molecular weight less than600 g/mole, or 550 g/mol, or 500 g/mole. Reactive diluents typicallycomprise one or two ethylenically unsaturated groups such as in the caseof mono(meth)acrylate or di(meth)acrylate monomers. In some embodiments,the filled dental composition comprises 0.5 to about 5 wt-% of reactivediluents. One suitable low viscosity reactive diluent is dodecanedioldimethacrylate (DDMA).

The hardenable dental composition may further comprise an additionfragmentation agent. The addition-fragmentation agent may comprise atleast one ethylenically unsaturated terminal group and a backbone unitcomprising an α, β-unsaturated carbonyl. The addition-fragmentationagent is free-radically cleavable. Without intending to be bound bytheory, it is surmised that the inclusion of such addition-fragmentationmaterial reduces the polymerization-induced stresses, such as by themechanism described in U.S. application Ser. No. 13/169,306, filed Jun.27, 2011. For embodiments wherein the AFM are multifunctional,comprising at least two ethylenically unsaturated group (e.g. Z is ≥2 inFormula I), the material can function as crosslinking agents, where thecrosslinks are labile.

The addition-fragmentation agents are preferably of the followingformula:

whereinR¹, R² and R³ are each independently Z_(m)-Q-, a (hetero)alkyl group ora (hetero)aryl group with the proviso that at least one of R¹, R² and R³is Z_(m)-Q-,Q is a linking group have a valence of m+1;Z is an ethylenically unsaturated polymerizable group,m is 1 to 6, preferably 1 to 2;each X¹ is independently —O— or —NR⁴—, where R⁴ is H or C₁-C₄ alkyl; andn is 0 or 1.

Addition-fragmentation agents according to Formula I are described inU.S. application Ser. No. 13/169,306, filed Jun. 27, 2011; incorporatedherein by reference.

The ethylenically unsaturated moiety, Z, of the monomer may include, butis not limited to the following structures, including (meth)acryloyl,vinyl, styrenic and ethynyl.

In some embodiments, Q is selected from —O—, —S—, —NR⁴—, —SO₂—, —PO₂—,—CO—, —OCO—, —R⁶—, —NR⁴—CO— NR⁴—, NR⁴—CO—O—, NR⁴—CO—NR⁴—CO—O—R⁶—,—CO—NR⁴—R⁶—, —R⁶—CO—O—R⁶—, —O—R⁶—. —S—R⁶—, —NR⁴—R⁶—, —SO₂—R⁶—, —PO₂—R⁶—,—CO—R⁶—, —OCO—R⁶—, —NR⁴—CO—R⁶—, NR⁴—R⁶—CO—O—, and NR⁴—CO—NR⁴—, whereineach R⁴ is hydrogen, a C₁ to C₄ alkyl group, or aryl group, each R⁶ isan alkylene group having 1 to 6 carbon atoms, a 5- or 6-memberedcycloalkylene group having 5 to 10 carbon atoms, or a divalent arylenegroup having 6 to 16 carbon atoms, with the proviso that Q-Z does notcontain peroxidic linkages.

In some embodiments, Q is an alkylene, such as of the formula—C_(r)H_(2r)—, where r is 1 to 10. In other embodiments, Q is ahydroxyl-substituted alkylene, such as —CH₂—CH(OH)—CH₂—. In someembodiments, Q is an aryloxy-substituted alkylene. In some embodiments,R⁵ is an alkoxy-substituted alkylene.

R¹—X¹— groups (and optionally R²—X²— groups) is typically selected fromH₂C═C(CH₃)C(O)—O—CH₂—CH(OH)—CH₂—O—,H₂C═C(CH₃)C(O)—O—CH₂—CH(O—(O)C(CH₃)═CH₂)—CH₂—O—,H₂C═C(CH₃)C(O)—O—CH(CH₂OPh)-CH₂—O—,H₂C═C(CH₃)C(O)—O—CH₂CH₂—N(H)—C(O)—O—CH(CH₂OPh)-CH₂—O—,H₂C═C(CH₃)C(O)—O—CH₂—CH(O—(O)C—N(H)—CH₂CH₂—O—(O)C(CH₃)C═CH₂)—CH₂—O—,H₂C═C(H)C(O)—O—(CH₂)₄—O—CH₂—CH(OH)—CH₂—O—,H₂C═C(CH₃)C(O)—O—CH₂—CH(O—(O)C—N(H)—CH₂CH₂—O—(O)C(CH₃)C═CH₂)—CH₂—O—,CH₃—(CH₂)₇—CH(O—(O)C—N(H)—CH₂CH₂—O—(O)C(CH₃)C═CH₂)—CH₂—O—,H₂C═C(H)C(O)—O—(CH₂)₄—O—CH₂—CH(—O—(O)C(H)═CH₂)—CH₂—O— andH₂C═C(H)C(O)—O—CH₂—CH(OH)—CH₂—O—.H₂C═C(H)C(O)—O—(CH₂)₄—O—CH₂—CH(—O—(O)C(H)═CH₂)—CH₂—O—, andCH₃—(CH₂)₇—CH(O—(O)C—N(H)—CH₂CH₂—O—(O)C(CH₃)C═CH₂)—CH₂—O—.

The polymerizable resin portion of the hardenable (i.e. polymerizable)dental composition described herein comprises at least 0.5 wt-%, or 1wt-%, 1.5 wt-%, or 2 wt-% of addition-fragmentation agent(s). Theaddition-fragmentation agent may comprise a single monomer or a blend oftwo or more addition-fragmentation agents. The total amount ofaddition-fragmentation agent(s) in the polymerizable resin portion ofthe hardenable (i.e. polymerizable) dental composition is typically nogreater than 30 wt-%, 25 wt-%, 20 wt-%, or 15 wt-%. As the concentrationof the addition-fragmentation monomer increases, the stress deflectionand Watts Shrinkage typically decrease. However, when the amount ofaddition-fragmentation agent exceeds an optimal amount, mechanicalproperties such as Diametral tensile strength and/or Barcol hardness, ordepth of cure may be insufficient.

Materials with high polymerization stress upon curing generate strain inthe tooth structure. One clinical consequence of such stress can be adecrease in the longevity of the restoration. The stress present in thecomposite passes through the adhesive interface to the tooth structuregenerating cuspal deflection and cracks in the surrounding dentin andenamel which can lead to postoperative sensitivity. Preferred (e.g.filled) dental compositions (useful for restorations such as fillingsand crowns) described herein typically exhibit a stress deflection of nogreater than 2.0, or 1.8, or 1.6, or 1.4, or 1.2 or 1.0 or 0.8 or 0.6microns.

In some embodiments, the total amount of addition-fragmentation agent(s)in the polymerizable resin portion of the hardenable (i.e.polymerizable) dental composition is no greater than 14 wt-%, 13 wt-%,or 12 wt-%, or 11 wt-%, or 10 wt-%.

Although a hardenable dental composition comprising an additionfragmentation agent in a low volume shrinkage composition typicallyprovides the lowest stress and/or lowest shrinkage, the fattymono(meth)acrylate can also improving the handling characteristics of adental composition comprising conventional hardenable (meth)acrylatemonomers.

In some embodiments, the hardenable dental composition comprises atleast one conventional hardenable (meth)acrylate monomers such asethoxylated bisphenol A dimethacrylate (BisEMA6), bisphenol A diglycidyldimethacrylate (bisGMA), urethane dimethacrylate (UDMA), andpolyethyleneglycol dimethacrylate (PEGDMMA). These monomers were foundto phase separate when formed into a mixture with (e.g. 5%, 10%, or 15%)stearyl mono(meth)acrylate. Bulk phase separation is a convenient way ofscreening the polymerization resin of the hardenable dental composition,or a component thereof, to determine the relative incompatibility.

Although 2-hydroxyethyl methacrylate (HEMA), triethlyene glycoldimethacrylate (TEGDMA), glycerol dimethacrylate (GDMA), and dodecandioldimethacrylate (DDMA), were found not to phase separate when combinedinto a mixture with (e.g. 20%) stearyl mono(meth)acrylate, these monomercan also be employed provided the polymerizable resin comprises asufficient amount of a monomer that does phase separate from theselected fatty mono(meth)acrylate.

The curable component of the curable dental composition can include awide variety of other ethylenically unsaturated compounds,epoxy-functional (meth)acrylate resins, vinyl ethers, and the like.

The (e.g., photopolymerizable) dental compositions may include freeradically polymerizable monomers, oligomers, and polymers having one ormore ethylenically unsaturated groups. Suitable compounds contain atleast one ethylenically unsaturated bond and are capable of undergoingaddition polymerization. Examples of useful ethylenically unsaturatedcompounds include acrylic acid esters, methacrylic acid esters,hydroxy-functional acrylic acid esters, hydroxy-functional methacrylicacid esters, and combinations thereof. Such free radically polymerizablecompounds include mono-, di- or poly-(meth)acrylates (i.e., acrylatesand methacrylates) such as, methyl (meth)acrylate, ethyl (meth)acrylate,isopropyl (meth)acrylate, n-hexyl (meth)acrylate, stearyl(meth)acrylate, allyl (meth)acrylate, glycerol tri(meth)acrylate,ethyleneglycol di(meth)acrylate, diethyleneglycol di(meth)acrylate,triethyleneglycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, 1,2,4-butanetrioltri(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, pentaerythritoltetra(meth)acrylate, sorbitol hex(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]p-propoxyphenyldimethylmethane, ethoxylatedbisphenolA di(meth)acrylate, and trishydroxyethyl-isocyanuratetri(meth)acrylate; (meth)acrylamides (i.e., acrylamides andmethacrylamides) such as (meth)acrylamide, methylenebis-(meth)acrylamide, and diacetone (meth)acrylamide; urethane(meth)acrylates; the bis-(meth)acrylates of polyethylene glycols(preferably of molecular weight 200-500); and vinyl compounds such asstyrene, diallyl phthalate, divinyl succinate, divinyl adipate anddivinyl phthalate. Other suitable free radically polymerizable compoundsinclude siloxane-functional (meth)acrylates. Mixtures of two or morefree radically polymerizable compounds can be used if desired.

The curable dental composition may also contain a monomer havinghydroxyl groups and ethylenically unsaturated groups in a singlemolecule. Examples of such materials include hydroxyalkyl(meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and2-hydroxypropyl (meth)acrylate; glycerol mono- or di-(meth)acrylate;trimethylolpropane mono- or di-(meth)acrylate; pentaerythritol mono-,di-, and tri-(meth)acrylate; sorbitol mono-, di-, tri-, tetra-, orpenta-(meth)acrylate; and2,2-bis[4-(2-hydroxy-3-ethacryloxypropoxy)phenyl]propane (bisGMA).Suitable ethylenically unsaturated compounds are available from a widevariety of commercial sources, such as Sigma-Aldrich, St. Louis.

The curable dental compositions may include resin-modified glassionomers cements such as those described in U.S. Pat. No. 5,130,347(Mitra) U.S. Pat. No. 5,154,762 (Mitra) U.S. Pat. No. 5,962,550(Akahane). Such compositions can be powder-liquid, paste-liquid orpaste-paste systems. Alternatively, copolymer formulations such as thosedescribed in U.S. Pat. No. 6,126,922 (Rozzi) are included in the scopeof the invention.

An initiator is typically added to the mixture of polymerizableingredients. The initiator is sufficiently miscible with the resinsystem to permit ready dissolution in (and discourage separation from)the polymerizable composition. Typically, the initiator is present inthe composition in effective amounts, such as from about 0.1 weightpercent to about 5.0 weight percent, based on the total weight of thecomposition.

The addition-fragmentation agent is generally free-radically cleavable.Although photopolymerization is one mechanism for generating freeradicals, other curing mechanisms also generate free radicals. Thus, theaddition-fragmentation agent does not require irradiation with actinicradiation (e.g. photocuring) in order to provide the reduction in stressduring curing.

In some embodiments, the mixture of monomers is photopolymerizable andthe composition contains a photoinitiator (i.e., a photoinitiatorsystem) that upon irradiation with actinic radiation initiates thepolymerization (or hardening) of the composition. Suchphotopolymerizable compositions can be free radically polymerizable. Thephotoinitiator typically has a functional wavelength range from about250 nm to about 800 nm. Suitable photoinitiators (i.e., photoinitiatorsystems that include one or more compounds) for polymerizing freeradically photopolymerizable compositions include binary and tertiarysystems. Typical tertiary photoinitiators include an iodonium salt, aphotosensitizer, and an electron donor compound as described in U.S.Pat. No. 5,545,676 (Palazzotto et al.). Iodonium salts include diaryliodonium salts, e.g., diphenyliodonium chloride, diphenyliodoniumhexafluorophosphate, and diphenyliodonium tetrafluoroboarate. Somepreferred photosensitizers may include monoketones and diketones (e.g.alpha diketones) that absorb some light within a range of about 300 nmto about 800 nm (preferably, about 400 nm to about 500 nm) such ascamphorquinone, benzil, furil, 3,3,6,6-tetramethylcyclohexanedione,phenanthraquinone and other cyclic alpha diketones. Of thesecamphorquinone is typically preferred. Preferred electron donorcompounds include substituted amines, e.g., ethyl4-(N,N-dimethylamino)benzoate.

Other suitable photoinitiators for polymerizing free radicallyphotopolymerizable compositions include the class of phosphine oxidesthat typically have a functional wavelength range of about 380 nm toabout 1200 nm. Preferred phosphine oxide free radical initiators with afunctional wavelength range of about 380 nm to about 450 nm are acyl andbisacyl phosphine oxides.

Commercially available phosphine oxide photoinitiators capable offree-radical initiation when irradiated at wavelength ranges of greaterthan about 380 nm to about 450 nm includebis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (IRGACURE 819, CibaSpecialty Chemicals, Tarrytown, N.Y.),bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl) phosphine oxide (CGI403, Ciba Specialty Chemicals), a 25:75 mixture, by weight, ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropan-1-one (IRGACURE 1700, Ciba SpecialtyChemicals), a 1:1 mixture, by weight, ofbis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropane-1-one (DAROCUR 4265, Ciba SpecialtyChemicals), and ethyl 2,4,6-trimethylbenzylphenyl phosphinate (LUCIRINLR8893X, BASF Corp., Charlotte, N.C.).

Tertiary amine reducing agents may be used in combination with anacylphosphine oxide. Illustrative tertiary amines include ethyl4-(N,N-dimethylamino)benzoate and N,N-dimethylaminoethyl methacrylate.When present, the amine reducing agent is present in thephotopolymerizable composition in an amount from about 0.1 weightpercent to about 5.0 weight percent, based on the total weight of thecomposition. In some embodiments, the curable dental composition may beirradiated with ultraviolet (UV) rays. For this embodiment, suitablephotoinitiators include those available under the trade designationsIRGACURE and DAROCUR from Ciba Speciality Chemical Corp., Tarrytown,N.Y. and include 1-hydroxy cyclohexyl phenyl ketone (IRGACURE 184),2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651),bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (IRGACURE 819),1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone(IRGACURE 369),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE907), and 2-hydroxy-2-methyl-1-phenyl propan-1-one (DAROCUR 1173).

The photopolymerizable compositions are typically prepared by admixingthe various components of the compositions. For embodiments wherein thephotopolymerizable compositions are not cured in the presence of air,the photoinitiator is combined under “safe light” conditions (i.e.,conditions that do not cause premature hardening of the composition).Suitable inert solvents may be employed if desired when preparing themixture. Examples of suitable solvents include acetone anddichloromethane.

Hardening is affected by exposing the composition to a radiation source,preferably a visible light source. It is convenient to employ lightsources that emit actinic radiation light between 250 nm and 800 nm(particularly blue light of a wavelength of 380-520 nm) such as quartzhalogen lamps, tungsten-halogen lamps, mercury arcs, carbon arcs, low-,medium-, and high-pressure mercury lamps, plasma arcs, light emittingdiodes, and lasers. In general, useful light sources have intensities inthe range of 0.200-1000 W/cm². A variety of conventional lights forhardening such compositions can be used.

The exposure may be accomplished in several ways. For example, thepolymerizable composition may be continuously exposed to radiationthroughout the entire hardening process (e.g., about 2 seconds to about60 seconds). It is also possible to expose the composition to a singledose of radiation, and then remove the radiation source, therebyallowing polymerization to occur. In some cases materials can besubjected to light sources that ramp from low intensity to highintensity. Where dual exposures are employed, the intensity of eachdosage may be the same or different. Similarly, the total energy of eachexposure may be the same or different.

The dental compositions comprising the multifunctional ethylenicallyunsaturated monomers may be chemically hardenable, i.e., thecompositions contain a chemical initiator (i.e., initiator system) thatcan polymerize, cure, or otherwise harden the composition withoutdependence on irradiation with actinic radiation. Such chemicallyhardenable (e.g., polymerizable or curable) composition are sometimesreferred to as “self-cure” compositions and may include redox curesystems. Further, the polymerizable composition may comprise acombination of different initiators, at least one of which is suitablefor initiating free radical polymerization.

The chemically hardenable compositions may include redox cure systemsthat include a polymerizable component (e.g., an ethylenicallyunsaturated polymerizable component) and redox agents that include anoxidizing agent and a reducing agent.

The reducing and oxidizing agents react with or otherwise cooperate withone another to produce free-radicals capable of initiatingpolymerization of the resin system (e.g., the ethylenically unsaturatedcomponent). This type of cure is a dark reaction, that is, it is notdependent on the presence of light and can proceed in the absence oflight. The reducing and oxidizing agents are preferably sufficientlyshelf-stable and free of undesirable colorization to permit theirstorage and use under typical conditions.

Useful reducing agents include ascorbic acid, ascorbic acid derivatives,and metal complexed ascorbic acid compounds as described in U.S. Pat.No. 5,501,727 (Wang et al.); amines, especially tertiary amines, such as4-tert-butyl dimethylaniline; aromatic sulfinic salts, such asp-toluenesulfinic salts and benzenesulfinic salts; thioureas, such as1-ethyl-2-thiourea, tetraethyl thiourea, tetramethyl thiourea,1,1-dibutyl thiourea, and 1,3-dibutyl thiourea; and mixtures thereof.Other secondary reducing agents may include cobalt (II) chloride,ferrous chloride, ferrous sulfate, hydrazine, hydroxylamine (dependingon the choice of oxidizing agent), salts of a dithionite or sulfiteanion, and mixtures thereof. Preferably, the reducing agent is an amine.

Suitable oxidizing agents will also be familiar to those skilled in theart, and include but are not limited to persulfuric acid and saltsthereof, such as sodium, potassium, ammonium, cesium, and alkyl ammoniumsalts. Additional oxidizing agents include peroxides such as benzoylperoxides, hydroperoxides such as cumyl hydroperoxide, t-butylhydroperoxide, and amyl hydroperoxide, as well as salts of transitionmetals such as cobalt (III) chloride and ferric chloride, cerium (IV)sulfate, perboric acid and salts thereof, permanganic acid and saltsthereof, perphosphoric acid and salts thereof, and mixtures thereof.

It may be desirable to use more than one oxidizing agent or more thanone reducing agent. Small quantities of transition metal compounds mayalso be added to accelerate the rate of redox cure. The reducing oroxidizing agents can be microencapsulated as described in U.S. Pat. No.5,154,762 (Mitra et al.). This will generally enhance shelf stability ofthe polymerizable composition, and if necessary permit packaging thereducing and oxidizing agents together. For example, through appropriateselection of an encapsulant, the oxidizing and reducing agents can becombined with an acid-functional component and optional filler and keptin a storage-stable state.

In favored embodiments, such as when the dental composition is employedas a dental restorative (e.g. dental filling or crown) or an orthodonticcement, the dental composition typically comprises appreciable amountsof (e.g. nanoparticle) filler. Such compositions preferably include atleast 40 wt-%, more preferably at least 45 wt-%, and most preferably atleast 50 wt-% filler, based on the total weight of the composition. Insome embodiments the total amount of filler is at most 90 wt-%,preferably at most 80 wt-%, and more preferably at most 75 wt-% filler.

The (e.g. filled) dental composite materials typically exhibit adiametral tensile strength (DTS) of at least about 70, 75, or 80 MPaand/or a Barcol Hardness of at least about 60, or 65, or 70-. The depthof cure ranges from about 4 to about 5 and comparable to commerciallyavailable (e.g. filled) dental compositions suitable for restorations.

Dental compositions suitable for use as dental adhesives can optionallyalso include filler in an amount of at least 1 wt-%, 2 wt-%, 3 wt-%, 4wt-%, or 5 wt-% based on the total weight of the composition. For suchembodiments, the total concentration of filler is at most 40 wt-%,preferably at most 20 wt-%, and more preferably at most 15 wt-% filler,based on the total weight of the composition.

Fillers may be selected from one or more of a wide variety of materialssuitable for incorporation in compositions used for dental applications,such as fillers currently used in dental restorative compositions, andthe like.

The filler can be an inorganic material. It can also be a crosslinkedorganic material that is insoluble in the polymerizable resin, and isoptionally filled with inorganic filler. The filler is generallynon-toxic and suitable for use in the mouth. The filler can beradiopaque, radiolucent, or nonradiopaque. Fillers as used in dentalapplications are typically ceramic in nature.

Non-acid-reactive inorganic filler particles include quartz (i.e.,silica), submicron silica, zirconia, submicron zirconia, andnon-vitreous microparticles of the type described in U.S. Pat. No.4,503,169 (Randklev).

The filler can also be an acid-reactive filler. Suitable acid-reactivefillers include metal oxides, glasses, and metal salts. Typical metaloxides include barium oxide, calcium oxide, magnesium oxide, and zincoxide. Typical glasses include borate glasses, phosphate glasses, andfluoroaluminosilicate (“FAS”) glasses. The FAS glass typically containssufficient elutable cations so that a hardened dental composition willform when the glass is mixed with the components of the hardenablecomposition. The glass also typically contains sufficient elutablefluoride ions so that the hardened composition will have cariostaticproperties. The glass can be made from a melt containing fluoride,alumina, and other glass-forming ingredients using techniques familiarto those skilled in the FAS glassmaking art. The FAS glass typically isin the form of particles that are sufficiently finely divided so thatthey can conveniently be mixed with the other cement components and willperform well when the resulting mixture is used in the mouth.

Generally, the average particle size (typically, diameter) for the FASglass is no greater than 12 micrometers, typically no greater than 10micrometers, and more typically no greater than 5 micrometers asmeasured using, for example, a sedimentation particle size analyzer.Suitable FAS glasses will be familiar to those skilled in the art, andare available from a wide variety of commercial sources, and many arefound in currently available glass ionomer cements such as thosecommercially available under the trade designations VITREMER, VITREBOND,RELY X LUTING CEMENT, RELY X LUTING PLUS CEMENT, PHOTAC-FIL QUICK,KETAC-MOLAR, and KETAC-FIL PLUS (3M ESPE Dental Products, St. Paul,Minn.), FUJI II LC and FUJI IX (G-C Dental Industrial Corp., Tokyo,Japan) and CHEMFIL Superior (Dentsply International, York, Pa.).Mixtures of fillers can be used if desired.

Other suitable fillers are disclosed in U.S. Pat. No. 6,387,981 (Zhanget al.) and U.S. Pat. No. 6,572,693 (Wu et al.) as well as PCTInternational Publication Nos. WO 01/30305 (Zhang et al.), U.S. Pat. No.6,730,156 (Windisch et al.), WO 01/30307 (Zhang et al.), and WO03/063804 (Wu et al.). Filler components described in these referencesinclude nanosized silica particles, nanosized metal oxide particles, andcombinations thereof. Nanofillers are also described in U.S. Pat. No.7,090,721 (Craig et al.), U.S. Pat. No. 7,090,722 (Budd et al.) and U.S.Pat. No. 7,156,911; and U.S. Pat. No. 7,649,029 (Kolb et al.).

Examples of suitable organic filler particles include filled or unfilledpulverized polycarbonates, polyepoxides, poly(meth)acrylates and thelike. Commonly employed dental filler particles are quartz, submicronsilica, and non-vitreous microparticles of the type described in U.S.Pat. No. 4,503,169 (Randklev).

Mixtures of these fillers can also be used, as well as combinationfillers made from organic and inorganic materials.

Fillers may be either particulate or fibrous in nature. Particulatefillers may generally be defined as having a length to width ratio, oraspect ratio, of 20:1 or less, and more commonly 10:1 or less. Fiberscan be defined as having aspect ratios greater than 20:1, or morecommonly greater than 100:1. The shape of the particles can vary,ranging from spherical to ellipsoidal, or more planar such as flakes ordiscs. The macroscopic properties can be highly dependent on the shapeof the filler particles, in particular the uniformity of the shape.

Micron-size particles are very effective for improving post-cure wearproperties. In contrast, nanoscopic fillers are commonly used asviscosity and thixotropy modifiers. Due to their small size, highsurface area, and associated hydrogen bonding, these materials are knownto assemble into aggregated networks.

In some embodiments, the dental composition preferably comprise ananoscopic particulate filler (i.e., a filler that comprisesnanoparticles) having an average primary particle size of less thanabout 0.100 micrometers (i.e., microns), and more preferably less than0.075 microns. As used herein, the term “primary particle size” refersto the size of a non-associated single particle. The average primaryparticle size can be determined by cutting a thin sample of hardeneddental composition and measuring the particle diameter of about 50-100particles using a transmission electron micrograph at a magnification of300,000 and calculating the average. The filler can have a unimodal orpolymodal (e.g., bimodal) particle size distribution. The nanoscopicparticulate material typically has an average primary particle size ofat least about 2 nanometers (nm), and preferably at least about 7 nm.Preferably, the nanoscopic particulate material has an average primaryparticle size of no greater than about 50 nm, and more preferably nogreater than about 20 nm in size. The average surface area of such afiller is preferably at least about 20 square meters per gram (m²/g),more preferably, at least about 50 m²/g, and most preferably, at leastabout 100 m²/g.

In some preferred embodiments, the dental composition comprises silicananoparticles. Suitable nano-sized silicas are commercially availablefrom Nalco Chemical Co. (Naperville, Ill.) under the product designationNALCO COLLOIDAL SILICAS. For example, preferred silica particles can beobtained from using NALCO products 1040, 1042, 1050, 1060, 2327 and2329.

Silica particles are preferably made from an aqueous colloidaldispersion of silica (i.e., a sol or aquasol). The colloidal silica istypically in the concentration of about 1 to 50 weight percent in thesilica sol. Colloidal silica sols that can be used are availablecommercially having different colloid sizes, see Surface & ColloidScience, Vol. 6, ed. Matijevic, E., Wiley Interscience, 1973. Preferredsilica sols for use making the fillers are supplied as a dispersion ofamorphous silica in an aqueous medium (such as the Nalco colloidalsilicas made by Nalco Chemical Company) and those which are low insodium concentration and can be acidified by admixture with a suitableacid (e.g. Ludox colloidal silica made by E. I. Dupont de Nemours & Co.or Nalco 2326 from Nalco Chemical Co.).

Preferably, the silica particles in the sol have an average particlediameter of about 5-100 nm, more preferably 10-50 nm, and mostpreferably 12-40 nm. A particularly preferred silica sol is NALCO 1041.

In some embodiments, the dental composition comprises zirconiananoparticles. Suitable nano-sized zirconia nanoparticles can beprepared using hydrothermal technology as described in U.S. Pat. No.7,241,437 (Davidson et al.).

In some embodiments, lower refractive index (e.g. silica) nanoparticlesare employed in combination with high refractive index (e.g. zirconia)nanoparticles in order to index match (refractive index within 0.02) thefiller to the refractive index of the polymerizable resin.

In some embodiments, the nanoparticles are in the form of nanoclusters,i.e. a group of two or more particles associated by relatively weakintermolecular forces that cause the particles to clump together, evenwhen dispersed in a hardenable resin.

Preferred nanoclusters can comprise a substantially amorphous cluster ofnon-heavy (e.g. silica) particles, and amorphous heavy metal oxide (i.e.having an atomic number greater than 28) particles such as zirconia. Theparticles of the nanocluster preferably have an average diameter of lessthan about 100 nm. Suitable nanocluster fillers are described in U.S.Pat. No. 6,730,156 (Windisch et al.); incorporated herein by reference.

In some preferred embodiments, the dental composition comprisesnanoparticles and/or nanoclusters surface treated with an organometalliccoupling agent to enhance the bond between the filler and the resin. Theorganometallic coupling agent may be functionalized with reactive curinggroups, such as acrylates, methacrylates, vinyl groups and the like.

Suitable copolymerizable organometallic compounds may have the generalformulas: CH₂═C(CH₃)_(m)Si(OR)_(n) or CH₂═C(CH₃)_(m)C═OOASi(OR)_(n);wherein m is 0 or 1, R is an alkyl group having 1 to 4 carbon atoms, Ais a divalent organic linking group, and n is from 1 to 3. Preferredcoupling agents include gamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,and the like.

In some embodiments, a combination of surface modifying agents can beuseful, wherein at least one of the agents has a functional groupco-polymerizable with a hardenable resin. Other surface modifying agentswhich do not generally react with hardenable resins can be included toenhance dispersibility or rheological properties. Examples of silanes ofthis type include, for example, aryl polyethers, alkyl, hydroxy alkyl,hydroxy aryl, or amino alkyl functional silanes.

The surface modification can be done either subsequent to mixing withthe monomers or after mixing. It is typically preferred to combine theorganosilane surface treatment compounds with nanoparticles beforeincorporation into the resin. The required amount of surface modifier isdependant upon several factors such as particle size, particle type,modifier molecular wt, and modifier type. In general it is preferredthat approximately a monolayer of modifier is attached to the surface ofthe particle.

The surface modified nanoparticles can be substantially fully condensed.Fully condensed nanoparticles (with the exception of silica) typicallyhave a degree of crystallinity (measured as isolated metal oxideparticles) greater than 55%, preferably greater than 60%, and morepreferably greater than 70%. For example, the degree of crystallinitycan range up to about 86% or greater. The degree of crystallinity can bedetermined by X-ray diffraction techniques. Condensed crystalline (e.g.zirconia) nanoparticles have a high refractive index whereas amorphousnanoparticles typically have a lower refractive index.

In some embodiments, the dental compositions can have an initial colorremarkably different than the cured dental structures. Color can beimparted to the composition through the use of a photobleachable orthermochromic dye. As used herein, “photobleachable” refers to loss ofcolor upon exposure to actinic radiation. The composition can include atleast 0.001 wt-% photobleachable or thermochromic dye, and typically atleast 0.002 wt-% photobleachable or thermochromic dye, based on thetotal weight of the composition. The composition typically includes atmost 1 wt-% photobleachable or thermochromic dye, and more typically atmost 0.1 wt-% photobleachable or thermochromic dye, based on the totalweight of the composition. The amount of photobleachable and/orthermochromic dye may vary depending on its extinction coefficient, theability of the human eye to discern the initial color, and the desiredcolor change. Suitable thermochromic dyes are disclosed, for example, inU.S. Pat. No. 6,670,436 (Burgath et al.).

For embodiments including a photobleachable dye, the color formation andbleaching characteristics of the photobleachable dye varies depending ona variety of factors including, for example, acid strength, dielectricconstant, polarity, amount of oxygen, and moisture content in theatmosphere. However, the bleaching properties of the dye can be readilydetermined by irradiating the composition and evaluating the change incolor. The photobleachable dye is generally at least partially solublein a hardenable resin.

Photobleachable dyes include, for example, Rose Bengal, MethyleneViolet, Methylene Blue, Fluorescein, Eosin Yellow, Eosin Y, Ethyl Eosin,Eosin bluish, Eosin B, Erythrosin B, Erythrosin Yellowish Blend,Toluidine Blue, 4′,5′-Dibromofluorescein, and combinations thereof.

The color change can be initiated by actinic radiation such as providedby a dental curing light which emits visible or near infrared (IR) lightfor a sufficient amount of time. The mechanism that initiates the colorchange in the compositions may be separate from or substantiallysimultaneous with the hardening mechanism that hardens the resin. Forexample, a composition may harden when polymerization is initiatedchemically (e.g., redox initiation) or thermally, and the color changefrom an initial color to a final color may occur subsequent to thehardening process upon exposure to actinic radiation.

Optionally, compositions may contain solvents (e.g., alcohols (e.g.,propanol, ethanol), ketones (e.g., acetone, methyl ethyl ketone), esters(e.g., ethyl acetate), other nonaqueous solvents (e.g.,dimethylformamide, dimethylacetamide, dimethylsulfoxide,1-methyl-2-pyrrolidinone)), and water.

If desired, the compositions can contain additives such as indicators,dyes, pigments, inhibitors, accelerators, viscosity modifiers, wettingagents, buffering agents, radical and cationic stabilizers (for exampleBHT), and other similar ingredients that will be apparent to thoseskilled in the art.

Additionally, medicaments or other therapeutic substances can beoptionally added to the dental compositions. Examples include, but arenot limited to, fluoride sources, whitening agents, anticaries agents(e.g., xylitol), calcium sources, phosphorus sources, remineralizingagents (e.g., calcium phosphate compounds), enzymes, breath fresheners,anesthetics, clotting agents, acid neutralizers, chemotherapeuticagents, immune response modifiers, thixotropes, polyols,anti-inflammatory agents, antimicrobial agents (in addition to theantimicrobial lipid component), antifungal agents, agents for treatingxerostomia, desensitizers, and the like, of the type often used indental compositions. Combinations of any of the above additives may alsobe employed. The selection and amount of any one such additive can beselected by one of skill in the art to accomplish the desired resultwithout undue experimentation.

The curable dental composition can be used to treat an oral surface suchas tooth, as known in the art. In some embodiments, the compositions canbe hardened by curing after applying the dental composition. Forexample, when the curable dental composition is used as a restorativesuch as a dental filling, the method generally comprises applying thecurable composition to an oral surface (e.g. cavity); and curing thecomposition. In some embodiments, a dental adhesive may be applied priorto application of the curable dental restoration material describedherein. Dental adhesives are also typically hardened by curingconcurrently with curing the highly filled dental restorationcomposition. The method of treating an oral surface may compriseproviding a dental article and adhering the dental article to an oral(e.g. tooth) surface.

In other embodiments, the compositions can be hardened (e.g.,polymerized) into dental articles prior to applying. For example, adental article such as a crown may be pre-formed from the hardenabledental composition described herein. Dental composite (e.g. crowns)articles can be made from the curable composition described herein bycasting the curable composition in contact with a mold and curing thecomposition. Alternatively, dental composite (e.g. crowns) article canbe made by first curing the composition forming a mill blank and thenmechanically milling the composition into the desired article.

Another method of treating a tooth surface comprises providing a dentalcomposition as described herein wherein the composition is in the formof a (partially hardened) hardenable, self-supporting, malleablestructure having a first semi-finished shape; placing the hardenabledental composition on a tooth surface in the mouth of a subject;customizing the shape of the hardenable dental composition; andhardening the hardenable dental composition. The customization can occurin the patient's mouth or on a model outside the patient mouth such asdescribed in U.S. Pat. No. 7,674,850 (Karim et al.); incorporated hereinby reference.

Objects and advantages are further illustrated by the followingexamples, but the particular materials and amounts thereof recited inthese examples, as well as other conditions and details, should not beconstrued to unduly limit this invention. Unless otherwise indicated,all parts and percentages are on a weight basis.

Examples

DDMA (Dodecanediol Sigma-Aldrich (St. Louis, MO) Dimethacrylate) StearylMethacrylate TCI America (Portland, OR) Lauryl MethacrylateSigma-Aldrich Methyl Methacrylate Sigma-Aldrich Pentyl MethacrylateSigma-Aldrich CPQ (camphorquinone) Sigma-Aldrich EDMAB (ethyl 4-(N,N-Sigma-Aldrich dimethylamino) benzoate) DPIHFP (diphenyl iodonium AlphaAesar (Ward Hill, MA) hexafluorophosphate) BHT (butylatedhydroxytoluene) Sigma-Aldrich YbF₃ (Ytterbium Fluoride), Sukgyung AT Co.Ltd., Korea 100 nanometer Silica filler Refers to a silane treatednano-sized silica having a nominal particle size of approximately 20nanometers, prepared essentially as described for Filler F in US PatentPublication No. 2005/0252413 Zirconia filler Refers to a silane treatednano-sized zirconia prepared essentially as de- scribed in PreparatoryExample 1A in US Patent Publication No. 2005/0252413 Zr—Si filler Refersto silane treated zirconia-silica nanocluster filler preparedessentially as described in Preparatory Examples A and B in U.S. Pat.No. 6,730,156Synthesis of Fatty Mono(Meth)AcrylatePreparation of Branched C20 Methacrylate

In a flask was mixed 100.0 g of Isofol 20 (Sasol), 59.46 g ofmethacrylic anhydride (Monomer and Polymer Dajac Lab), 1.0 g of4-dimetylamino pyridine (Aldrich), and 100 mL of ethyl acetate. Themixture was stirred at 60° C. for 17 hours, then for an additional 7hours at 90° C. The mixture was diluted with 200 mL of ethyl acetate,then washed with 1.0 M HCl, and 1.0 M NaOH. The organic layer was thenconcentrated under vacuum. The crude oil was mixed with an equal portionof hexane and passed through a column of neutral alumina to removecolored impurities. The alumina was eluted with hexane. The collectedfractions were concentrated under vacuum to give the final product,depicted as follows, as a colorless oil.

Preparation of Branched C18 Acrylate

A mixture of 197.17 g of Isofol 18T (Sasol), 78.12 g of triethylamine(TEA, Alfa Aesar), and 700 g of methylene chloride (MC) was cooled to 5°C. using an ice bath. 69.86 g of acryloyl chloride (AC, Alfa Aesar) wasadded dropwise over one hour with mechanical stirring. After 10 hours,the mixture was filtered, then concentrated under vacuum. The remainingoil was diluted with ethyl acetate and washed with 1.0 M HCl, 1.0 MNaOH, and brine. The organic layer was then concentrated under vacuum.The crude oil was mixed with an equal portion of hexane and passedthrough a column of neutral alumina to remove colored impurities. Thealumina was eluted with hexane. The collected filtrate was concentratedunder vacuum to give the final product as a colorless oil.

This gives a mixture of acrylate isomers as follows wherein the averagealkyl group is C18.

-   2-hexyl-1-decyl acrylate,-   2-octyl-1-decyl acrylate,-   2-hexyl-1-dodecyl acrylate,-   2-octyl-1-dodecyl acrylate    Synthesis of Polymerizable Monomers    1. Synthesis of Addition Fragmentation Agent (AFM-1)    Distillation of Methyl Methacrylate Oligomer Mixture

Distillation was performed as described in Moad, C. L.; Moad, G.;Rizzardo, E.; and Thang, S. H. Macromolecules, 1996, 29, 7717-7726, withdetails as follows: A 1 L round-bottomed flask equipped with a magneticstir bar was charged with 500 g of methyl methacrylate oligomer mixture.The flask was fitted with a Vigreux column, a condenser, a distributionadapter, and four collection flasks. With stirring, the distillationapparatus was placed under reduced pressure (0.25 mm Hg). The oligomermixture was stirred under reduced pressure at room temperature until gasevolution (removal of methyl methacrylate monomer) had largely subsided.The distillation pot was then heated to reflux in an oil bath to distillthe oligomer mixture. The fractions isolated by this procedure arelisted in Table 1.

TABLE 1 Fractions from the Distillation of Methyl Methacrylate OligomerMixture Pressure Boiling point Mass Approximate Fraction (mm Hg) (° C.)(g) Composition A 0.25 59 63.27 Dimer B 0.09 47 115.97 Dimer C 0.1060-87 25.40 dimer (~50-75%), oligomers (mainly trimer) D 0.10 87 15.20dimer (~5%), oligomers (mainly trimer) E 0.13 105  156.66 oligomers(trimer and higher)Hydrolysis of Methyl Methacrylate Dimer

Hydrolysis of the dimer to Diacid 1 was performed as described inHutson, L.; Krstina, J.; Moad, G.; Morrow, G. R.; Postma, A.; Rizzardo,E.; and Thang, S. H. Macromolecules, 2004, 37, 4441-4452, with detailsas follows: A 1 L, round-bottomed flask equipped with a magnetic stirbar was charged with deionized water (240 mL) and potassium hydroxide(60.0 g, 1007 mmol). The mixture was stirred until homogeneous. Methylmethacrylate dimer (75.0 g, 374.6 mmol) was added. The reaction wasequipped with a reflux condenser and was heated to 90° C. in an oilbath. After 17 hours, the reaction was removed from the oil bath and wasallowed to cool to room temperature. The reaction solution was acidifiedto pH of approximately 1 using concentrated HCl. A white precipitateformed upon acidification. The heterogeneous mixture was vacuum filteredand quickly washed twice with 50-100 mL of deionized water. The whitesolid was dried by pulling air through the solid for approximately 4hours. The white solid was then dissolved in approximately 1750 mL ofdichloromethane. Only a very small amount (less than a gram) of solidremained insoluble. The solution was allowed to stand for 24 hours. Thedichloromethane solution was then vacuum filtered to remove theundissolved white solid. The filtered dichloromethane solution wasconcentrated in vacuo to provide a white solid. The solid was furtherdried under high vacuum to provide Diacid 1 (55.95 g, 325.0 mmol, 87%)as a white powder.

Preparation of AFM-1

An approximately 250 mL amber bottle equipped with a magnetic stir barwas charged with glycidyl methacrylate (23.0 mL, 24.8 g, 174 mmol) andtriphenyl antimony (0.369 g, 1.04 mmol). The reaction was covered with aplastic cap with two 16 gauge needles pierced through the cap to allowair into the reaction. With stirring, the mixture was heated to 100° C.in an oil bath. Diacid 1 (15.0 g, 87.1 mmol) was added to the reactionin small portions over a period of 1.5 hours. After 21 hours, triphenylphosphine (0.091 g, 0.35 mmol) was added. The reaction was kept stirringat 100° C. After an additional 6.5 hours the reaction was sampled, and1H NMR analysis was consistent with the desired product as a mixture ofisomers and indicated consumption of glycidyl methacrylate. The reactionwas cooled to room temperature to provide AFM-1 as a clear, very paleyellow viscous material.

2. Synthesis of Isocyanurate Trimer

Phthalic acid anhydride (57.0 g, 0.385 mol, CAS #85-33-9, Alfa Aesar,lot G30T004), 4-(dimethylamino)pyridine (DMAP, 4.9 g, 0.04 mol, CAS#1122-58-3, Alfa Aesar, lot L125009), 2-hydoxyethylmethacrylate (HEMA,50.9 g, 0.391 mol, and butylated hydroxytoluene (BHT, 0.140 g) werecharged into a 2-liter 3-neck reaction flask equipped with a mechanicalstirrer, a thermocouple connected to a temperature controller, a dry airstream running through a T-shape connection into the reactor then to anoil bubbler, and a heating mantle. With continuous stirring, the flaskcontents were heated to 95° C., by which all components dissolved and aclear liquid was obtained. Heating at 95° C. and stirring were continuedfor 5 hours. The heat was turned off and the flask contents were allowedto cool to room temperature while still being stirred under dry air.Acetone (250 ml) was added followed by tris-(2-hydroxyethyl)isocyanurate(33.58 g, 0.158 mol, from TCI). The heating mantle was replaced with anice bath, where the mixture was cooled to 0-5° C. A solution made fromdicyclohexyl carbodiimide (DCC, 81 g, 0.393 mol) in 120 ml acetone wasplaced into a 500 ml dropping funnel which was placed in-between thereaction flask and the dry air in-let. The DCC solution was added slowlyto the continuously stirred reaction mixture in a rate where thereaction mixture temperature would not exceed 10° C. After completeaddition of the DCC solution, the reaction was stirred in the ice bathfor 2 hours in at room temperature overnight. On day 2, the solid formedwas removed by vacuum filtration and the residue was concentrated in arotary evaporator at 40-45° C. bath. The residue was dissolved in 300 mlsolution of ethylacetate:hexanes, 2:1 by volume. The obtained solutionwas extracted with 200 ml of 1.0 N. HCl, 200 ml of 10% aqueous, 200 mlH₂O, and 200 ml brine. The organic layer was concentrated in a rotaryevaporator with 40° C. bath. Further drying was done under a vacuum pumpat 50° C. for 3 hours with air bleeding into the product during thewhole time to give an almost colorless hazy viscous liquid.

The refractive index was measured and found to be 1.5386. By use of NMRthe liquid was determined to be the product shown is the followingreaction scheme.

The calculated molecular weight of the depicted end product wasdetermined to be 1041 g/mole.

3. ERGP-IEM was Made as Described in WO2012/003136.

Test MethodsDiametral Tensile Strength (DTS) Test Method

Diametral tensile strength of a test sample was measured according tothe following procedure. An uncured composite sample was injected into a4-mm (inside diameter) glass tube; the tube was capped with siliconerubber plugs. The tube was compressed axially at approximately 2.88kg/cm′ pressure for 5 minutes. The sample was then light cured for 80seconds by exposure to a XL 1500 dental curing light (3M Company, St.Paul, Minn.), followed by irradiation for 90 seconds in a Kulzer UniXScuring box (Heraeus Kulzer GmbH, Germany). The sample was cut with adiamond saw to form disks about 2 mm thick, which were stored indistilled water at 37° C. for about 24 hours prior to testing.Measurements were carried out on an Instron tester (Instron 4505,Instron Corp., Canton, Mass.) with a 10 kilonewton (kN) load cell at acrosshead speed of 1 mm/minute according to ISO Specification 7489 (orAmerican Dental Association (ADA) Specification No. 27). Samples wereprepared and measured with results reported in MPa as the average ofmultiple measurements.

Depth of Cure Test Method

The depth of cure was determined by filling a 10 or 15 millimeterstainless steel mold cavity with the composite, covering the top andbottom of the mold with sheets of polyester film, pressing the sheets toprovide a leveled composition surface, placing the filled mold on awhite background surface, irradiating the dental composition for 20seconds using a dental curing light (3M Dental Products Curing Light2500 or 3M ESPE Elipar FreeLight2, 3M ESPE Dental Products), separatingthe polyester films from each side of the mold, gently removing (byscraping) materials from the bottom of the sample (i.e., the side thatwas not irradiated with the dental curing light), and measuring thethickness of the remaining material in the mold. The reported depths arethe actual cured thickness in millimeters divided by 2.

Extrusion Force Test Method

Extrusion force was tested using an Instron Model 4505 (Instron Corp.,Canton, Mass.) and a crosshead speed of 51 mm/min. A cylindrical nyloncapsule having internal dimensions of 4.0 mm diameter by 23.0 mm lengthand having an angled dispensing tip with an internal diameter of 2.0 mmand length of 6.8 mm was loaded with a composite paste, a plunger wasinserted into the capsule, and the assembled capsule was loaded into asample holder such that the capsule body was supported on the stationaryjaw and the plunger was pushed by the moveable jaw. As the plunger waspushed into the capsule, the maximum load (extrusion force) requiredwhile pushing the plunger into the capsule was measured in units ofkilogram-force (Kg-F).

Contrast Ratio

Paste samples were formed into 1 mm thick by 20 mm diameter disks andcured by exposing them to illumination from an LED array (455 nmwavelength, 800 mW/cm² intensity) for 20 seconds on one side of thedisk. ASTM-D2805-95 test method was modified to measure the ContrastRatio (or opacity) of the disks. Y-tristimulus values for the disks weremeasured on an Ultrascan XE Colorimeter (Hunter Associates Laboratory,Reston, Va.) with a 0.953-cm aperture using separate white and blackbackgrounds. The D65 Illuminant was used with no filters for allmeasurements. A 10 degree angle of view was used. The Contrast Ratio,CR, was calculated as the ratio of the reflectance through a material ona black substrate to the reflectance through an identical material on awhite substrate. Reflectance is defined as equal to the Y-tristimulusvalue. Thus, CR=RB/RW, where RB=reflectance through a sample on a blacksubstrate and RW=reflectance through the same sample on a whitesubstrate. Reported Contrast Ratio values are from single measurementswith lower values indicative of greater translucency (i.e., transmissionof light).

Polymerizable Resin Compositions Examples 1A-2A

grams, (wt % of polymerizable resin, wt % of total hardenablecomposition including filler)

Comparative Resin for Resin for Component resin Example 1A Example 2AStearyl 0.0000 (0.00, 0.00) 0.9828 (4.90, 1.76) 1.9646 (4.91, 1.31)methacrylate Trimer  18.362 (30.52, 11.60)  5.6668 (28.28, 10.18)11.6448 (29.11, 7.79) ERGP-IEM  35.938 (59.73, 22.70)  11.500 (57.39,20.66)  23.2895 (58.22, 15.59) DDMA  3.827 (6.36, 2.42)  1.185 (5.91,2.13) 2.3551 (5.89, 1.58) BHT 0.0322 (0.05, 0.02) 0.0126 (0.06, 0.02)0.0199 (0.05, 0.01) AFM-1  0.911 (1.51, 0.57)  0.326 (1.63, 0.59) 0.0000(0.00, 0.00) CPQ 0.1922 (0.32, 0.12) 0.0646 (0.32, 0.12) 0.1279 (0.32,0.09) EDMAB 0.6039 (1.00, 0.38) 0.1996 (1.00, 0.36) 0.3998 (1.00, 0.27)DPIHFP 0.3051 (0.51, 0.19) 0.1002 (0.50, 0.18) 0.1990 (0.50, 0.13)Dental Restoration Composition Examples 1B-2B

grams, (wt % of total hardenable composition including filler)

Component Comparative Example 1B Example 2B Comparative  2.8651 (38.01)0.0000 (0.00) 0.0000 (0.00) resin Resin for 0.0000 (0.00)   7.20 (36.00)0.0000 (0.00) Example 1 Resin for 0.0000 (0.00) 0.0000 (0.00)  5.361(26.77) Example 2 YbF₃ 0.3501 (4.64)  0.96 (4.80) 1.0973 (5.48) Silicafiller 0.2734 (3.63) 0.4995 (2.50) 0.5719 (2.86) Zirconia filler 0.1464(1.94) 0.2695 (1.35) 0.3317 (1.66) Zr/Si filler  3.9036 (51.78) 11.0723(55.36) 12.6679 (63.25)Handling Test Results for Examples 1-2Comparative Paste:

a dental instrument would push into the material and stick, rather thanmoving the material. The paste was extremely sticky and would stringwith the instrument, often over an inch when the instrument was pulledback.

Example 1 Paste

The material could be moved by an instrument, could be shaped, allowinganatomy to be formed in the paste before curing. The stringing andtackiness were both substantially reduced.

Example 2 Paste

This paste was a universal composite, rather than a flowable, because ofthe % filler loading. The paste had exceptional ability to feather, orthin to a fine layer with a dental instrument, it held its shape aftermanipulation, and had a high surface gloss. The stringing and tackinesswere both substantially reduced.

Dental Restoration Composition Examples 3-6

grams, (wt-% of total composition including filler)

Comparative Component (grams) Example 3 Example 4 Example 5 Example 6Stearyl 0.0000 (0.00) 0.1081 (0.54) 0.1622 (0.81) 0.2162 (1.08) 0.2703(1.35) methacrylate Trimer 1.6448 (8.22) 1.6119 (8.05) 1.5955 (7.97)1.5790 (7.89) 1.5626 (7.81) ERGP-IEM  3.2355 (16.17)  3.1708 (15.84) 3.1384 (15.68)  3.1061 (15.52)  3.0737 (15.36) DDMA 0.3446 (1.72)0.3377 (1.69) 0.3343 (1.67) 0.3308 (1.65) 0.3274 (1.64) BHT 0.0027(0.01) 0.0026 (0.01) 0.0026 (0.01) 0.0026 (0.01) 0.0026 (0.01) AFM-10.0797 (0.40) 0.0781 (0.39) 0.0773 (0.39) 0.0765 (0.38) 0.0757 (0.38)CPQ 0.0174 (0.09) 0.0171 (0.09) 0.0169 (0.08) 0.0167 (0.08) 0.0165(0.08) EDMAB 0.0541 (0.27) 0.0530 (0.26) 0.0525 (0.26) 0.0519 (0.26)0.0514 (0.26) DPIHFP 0.0270 (0.13) 0.0265 (0.13) 0.0262 (0.13) 0.0259(0.13) 0.0257 (0.13) YbF₃ 1.0955 (5.48)  1.10 (5.50)  1.10 (5.50)  1.10(5.50)  1.10 (5.50) Silica filler 0.5696 (2.85)  0.57 (2.85)  0.57(2.85)  0.57 (2.85)  0.57 (2.85) Zirconia filler 0.3061 (1.53)  0.31(1.55)  0.31 (1.55)  0.31 (1.55)  0.31 (1.55) Zr/Si filler 12.6295(63.13)  12.63 (63.10)  12.63 (63.10)  12.63 (63.10)  12.63 (63.10)Test Results for Examples 3-6

Composition Contrast Ratio Comparative 35.31 Example 3 37.16 Example 446.26 Example 5 51.77 Example 6 56.31Polymerizable Resin Composition Examples 7-12 all quantities are ingrams

Component Comp. Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 0.0000 0.27030.2703 0.2703 0.2703 0.2703 0.2703 No fatty Methyl Pentyl Lauryl StearylBranched Branched mono methacrylate methacrylate methacrylatemethacrylate C18 C20 (meth) Acrylate Methacrylate acrylate Trimer 1.64481.5626 1.5626 1.5626 1.5626 1.5626 1.5626 ERGP-IEM 3.2355 3.0737 3.07373.0737 3.0737 3.0737 3.0737 DDMA 0.3446 0.3274 0.3274 0.3274 0.32740.3274 0.3274 BHT 0.0027 0.0026 0.0026 0.0026 0.0026 0.0026 0.0026 AFM-10.0797 0.0793 0.0793 0.0793 0.0793 0.0793 0.0793 CPQ 0.0174 0.01650.0165 0.0165 0.0165 0.0165 0.0165 EDMAB 0.0541 0.0514 0.0514 0.05140.0514 0.0514 0.0514 DPIHFP 0.0270 0.0256 0.0256 0.0256 0.0256 0.02560.0256

The polymerizable resin mixtures (i.e. without filler) were thoroughlymixed at elevated temperatures and allowed to cool to room temperature,observing phase separation behavior.

Phase separation was seen in Examples 10-12, while no phase separationwas seen in Examples 7 and 8. In the case of Example 9, comprisinglauryl methacrylate, the mixture needed cooling to 5 degrees C. toobserve phase separation.

Dental Restoration Composition Examples 13-20

grams, (wt % of total composition including filler)

Component Comp. Ex. Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex.20 Fatty mono 0.0000 0.2725 0.5404 0.8100 1.0839 0.2745 0.5383 0.80511.0722 methacrylate (0.00) (1.36) (2.70) (4.05) (5.42) (1.37) (2.69)(4.03) (5.36) Stearyl Stearyl Stearyl Stearyl Lauryl Lauryl LaurylLauryl Trimer 1.6448 1.5580 1.4751 1.3934 1.3107 1.5610 1.4757 1.39251.3083 (8.22) (7.79) (7.38) (6.96) (6.55) (7.80) (7.38) (6.96) (6.55)ERGP-IEM 3.2355 3.0648 2.9017 2.7410 2.5783 3.0708 2.9029 2.7392 2.5737(16.17) (15.33) (14.51) (13.70) (12.88) (15.35) (14.52) (13.70) (12.88)DDMA 0.3446 0.3264 0.3091 0.2919 0.2746 0.3271 0.3092 0.2917 0.2741(1.72) (1.63) (1.55) (1.46) (1.37) (1.63) (1.55) (1.46) (1.37) BHT0.0027 0.0026 0.0024 0.0023 0.0022 0.0026 0.0024 0.0023 0.0021 (0.01)(0.01) (0.01) (0.01) (0.01) (0.01) (0.01) (0.01) (0.01) AFM-1 0.07970.0755 0.0715 0.0675 0.0635 0.0756 0.0715 0.0675 0.0634 (0.40) (0.38)(0.36) (0.34) (0.32) (0.38) (0.36) (0.34) (0.32) CPQ 0.0174 0.01720.0173 0.0173 0.0173 0.0174 0.0173 0.0173 0.0173 (0.09) (0.09) (0.09)(0.09) (0.09) (0.09) (0.09) (0.09) (0.09) EDMAB 0.0541 0.0541 0.05390.0540 0.0539 0.0541 0.0541 0.0538 0.0539 (0.27) (0.27) (0.27) (0.27)(0.27) (0.27) (0.27) (0.27) (0.27) DPIHFP 0.0270 0.0270 0.0269 0.02690.0271 0.0270 0.0268 0.0270 0.0270 (0.13) (0.14) (0.13) (0.13) (0.14)(0.13) (0.13) (0.14) (0.14) YbF₃ 1.0955 1.0900 1.0967 1.0995 1.09501.0951 1.0950 1.0949 1.0950 (5.48) (5.45) (5.48) (5.50) (5.47) (5.47)(5.48) (5.48) (5.48) Silica filler 0.5696 0.5695 0.5695 0.5694 0.56990.5699 0.5698 0.5695 0.5690 (2.85) (2.85) (2.85) (2.85) (2.85) (2.85)(2.85) (2.85) (2.85) Zirconia 0.3061 0.3063 0.3061 0.3069 0.3060 0.30660.3070 0.3061 0.3062 filler (1.53) (1.53) (1.53) (1.53) (1.53) (1.53)(1.54) (1.53) (1.53) Zr/Si filler 12.6295 12.6249 12.6288 12.626812.6280 12.6263 12.6280 12.6309 12.6270 (63.13) (63.16) (63.15) (63.11)(63.11) (63.11) (63.15) (63.16) (63.17)Test Results for Examples 13-20

Depth Contrast Extrusion force DTS (MPa) Contrast of cure Ratio/Depth(Max Load, KgF) Example (Std. Dev.) Ratio (mm) of Cure (Std. Dev.)Control 73.154 (3.662) 39.03 5.41 7.21 11.664 (1.916)  13 69.089 (3.227)56.48 4.33 13.04 8.999 (1.717) 14 63.302 (2.191) 61.56 3.71 16.59 10.243(1.044)  15 54.741 (2.737) 66.07 3.36 19.66 7.254 (0.856) 16 50.797(3.942) 67.52 3.13 21.57 7.749 (1.601) 17 70.028 (3.04)  36.07 6.07 5.943.609 (0.336) 18 66.279 (3.841) 42.35 5.10 8.30 2.203 (0.309) 19 64.702(2.692) 59.59 3.79 15.72 2.616 (0.327) 20 56.552 (1.606) 66.59 3.3519.87 2.580 (0.268 Polymerizable Resin Composition Example 21A

Resin composition, grams, (wt % of resin, wt % of total compositionincluding filler)

Stearyl methacrylate 0.9960 (4.97, 1.33) Trimer  5.7543 (28.72, 7.67)ERGP-IEM  11.6910 (58.34, 15.59) DDMA 1.2117 (6.05, 1.62) BHT  0.0023(0.01, 0.003) AFM-1 0.3027 (1.51, 0.40) CPQ 0.0142 (0.07, 0.02) EDMAB0.0419 (0.21, 0.06) DPIHFP 0.0252 (0.13, 0.03)Dental Restoration Composition 21B

grams, (wt % of total composition including filler)

Component Comparative paste Resin mixture  6.6874 (26.72) YbF₃ 1.3807(5.52) Silica filler 0.7225 (2.89) Zirconia filler 0.3931 (1.57) Zr/Sifiller 15.8478 (63.31)

The paste composition was formed into a 1 mm thick disk by placing thecomposite paste between two pieces of Mylar film spaced 1 mm apart andcuring for 20 seconds with an LED array. Transmission electronmicroscopy was used to generate the image shown as FIG. 1, which showsthe phase separated domains of stearyl methacrylate as lighter circularareas.

What is claimed is:
 1. A hardenable dental composition comprising: apolymerizable resin composition comprising at least one multifunctionalethylenically unsaturated monomer; 0.2 to 10 wt-% of one or more fattymono(meth)acrylate monomers; and at least 50 wt-% of inorganic oxidefiller, wherein the fatty mono(meth)acrylate monomer is phase separatedfrom the polymerizable resin composition such that the fattymono(meth)acrylate monomer is in the form of microscopic domains.
 2. Thehardenable dental composition of claim 1 wherein the hardenable dentalcomposition can be shaped with an instrument without substantiallystringing.
 3. The hardenable dental composition of the claim 1 whereinthe fatty mono(meth)acrylate monomer comprises an alkyl group havinggreater than 12 carbon atoms.
 4. The hardenable dental composition ofthe claim 1 wherein the fatty mono(meth)acrylate monomer comprises analkyl group having 6 to 12 carbon atoms.
 5. The hardenable dentalcomposition of claim 1 wherein the inorganic oxide filler comprisesnanoparticles.
 6. The hardenable dental composition of claim 5 whereinthe nanoparticles comprise silica, zirconia, or mixtures thereof.
 7. Thehardenable dental composition of claim 5 wherein the nanoparticles arein the form of nanoclusters.
 8. The hardenable dental composition ofclaim 5 wherein hardenable dental composition can be extruded through anorifice with a force no greater than 20 kg for an orifice diameter of 2mm.
 9. The hardenable dental composition of claim 1 wherein the fattymono(meth)acrylate increases the contrast ratio of the hardenable dentalcomposition by at least
 5. 10. The hardenable dental composition ofclaim 1 wherein the hardenable dental composition has a contrast ratioof at least 45 and is free of opacifying pigment.
 11. The hardenabledental composition of claim 1 wherein the hardenable dental compositionhas a ratio of contrast ratio to depth of cure of at least
 10. 12. Thehardenable dental composition of claim 1 wherein the polymerizable resincomposition comprises one or more ethylenically unsaturated monomersselected from the group consisting of isocyanurate monomers, ethoxylatedresorcinol monomers, and mixtures thereof.
 13. The hardenable dentalcomposition of claim 1 wherein the polymerizable resin compositioncomprises an addition-fragmentation agent.
 14. The hardenable dentalcomposition of claim 1 wherein the polymerizable resin compositioncomprises at least one monomer selected from the group consisting ofethoxylated bisphenol A dimethacrylate (BisEMA6), bisphenol A diglycidyldimethacrylate (bisGMA), urethane dimethacrylate (UDMA), andpolyethyleneglycol dimethacrylate (PEGDMA).
 15. A dental articlecomprising the hardenable dental composition of claim 1 at leastpartially hardened.
 16. A hardened dental composition comprising: apolymerized resin composition comprising at least one multifunctionalethylenically unsaturated monomer; 0.2 to 10 wt-% of one or more fattymono(meth)acrylate monomers; and at least 50 wt-% of inorganic oxidefiller, wherein the fatty mono(meth)acrylate monomer is phase separatedfrom the polymerized resin composition such that the fattymono(meth)acrylate monomer is in the form of microscopic domains.